using System.Collections.Immutable;
using HermesSocketLibrary.db;

namespace HermesSocketServer.Store.Internal
{
    public abstract class AutoSavedStore<K, V> : GroupSaveStore<K, V> where K : class where V : class
    {
        private readonly GroupSaveSqlGenerator<V> _generator;
        private readonly DatabaseTable _table;
        private readonly Database _database;
        private readonly Serilog.ILogger _logger;


        public AutoSavedStore(DatabaseTable table, Database database, Serilog.ILogger logger)
            : base(logger)
        {
            _generator = new GroupSaveSqlGenerator<V>(table.PropertyMapping, logger);
            _table = table;
            _database = database;
            _logger = logger;
        }

        public override async Task Save()
        {
            var allColumns = _table.KeyColumns.Union(_table.DataColumns).ToArray();

            await GenerateQuery(_added, 
                (size) => _generator.GeneratePreparedInsertSql(_table.TableName, size, allColumns),
                async (query, _, values) => await _generator.DoPreparedStatement(_database, query, values, allColumns));
            
            await GenerateQuery(_modified, 
                (size) => _generator.GeneratePreparedUpdateSql(_table.TableName, size, _table.KeyColumns, _table.DataColumns),
                async (query, _, values) => await _generator.DoPreparedStatement(_database, query, values, allColumns));

            await GenerateQuery(_deleted, 
                (size) => _generator.GeneratePreparedDeleteSql(_table.TableName, size, _table.KeyColumns),
                async (query, keys, _) => await _generator.DoPreparedStatementRaw(_database, query, keys, _table.KeyColumns));
        }

        private async Task GenerateQuery(IList<K> keys, Func<int, string> generate, Func<string, IEnumerable<K>, IEnumerable<V>, Task> execute)
        {
            ImmutableList<K>? list = null;
            lock (_lock)
            {
                if (!keys.Any())
                    return;

                list = keys.ToImmutableList();
                keys.Clear();
            }

            var query = generate(list.Count);
            _logger.Debug($"{_table.TableName} - Adding {list.Count} rows to database: {query}");

            var values = list.Select(id => _store[id]).Where(v => v != null);
            await execute(query, list, values);
        }
    }
}